Drilling bit for earth formations

ABSTRACT

A drilling bit for earth formations that are relatively difficult to drill that incorporate a body portion having a matrix thereon and defining a smooth annular cutting face of a configuration defining an annular line of tangency with a plane disposed in substantially normal relation to the axis of a bore hole being drilled by the bit. A plurality of cutting elements, such as industrial diamonds, are embedded in the matrix and include cutting portions thereof extending beyond the matrix for cutting engagement with the formation being drilled. The cutting elements are oriented in rows radiating from a coolant aperture formed centrally of the bit outwardly about the entire cutting face defined by the matrix. The cutting elements are arranged to create closely spaced generally circular scratches in the formation for erosion thereof as the bit is rotated relative to the formation. A plurality of coolant courses are formed in the matrix and extend from the coolant passage in radiating manner and terminate radially inwardly of said annular line of tangency thereby causing the velocity of the coolant fluid to increase materially as it is evenly distributed in the form of a relatively thin high velocity film flowing over the entire smooth matrix surface disposed radially outwardly of the coolant courses for efficient cooling of each of the cutting elements and removal of cuttings eroded from the formation by the cutting elements.

United States Patent Y [1 .1 short [451 July23, i974 [73] Assignee: Williams Diamond Bits, Division of Smith International, Greenville, Tex.

22 Filed:' Oct. 31, 1972 21 Appl.N0.:302,544

[52] US. Cl. 175/65, 175/329 [51] Int. Cl E2lb 9/36 [58] Field of Search 175/329, 330, 409, 410, 175/65 [56] References Cited 7 UNITED STATES PATENTS 2,838,284 6/1958 Austin 175/329 3,135,341 6/1964. Ritter 175/329 3,599,736 8/1971 Thompson 175/329 3,640,355 12/1972 Lebourg 175/329 3,693,735 9/1972 Cortes 175/329 3,709,308 1/1973 Rowley et a Primary Examiner-David H. Brown [5 7] ABSTRACT A drilling bit for earth formations that are relatively difficult to drill that incorporate a body portion having i a matrix thereon and defining ,a smooth annular cut ting face of a configuration defining an annular line of tangency with a plane disposed in substantially normal relation to'the axis of a bore hole being drilled by the bit. A plurality of cutting elements, such as industrial diamonds, are embedded in the matrixand include cutting portions thereof extending beyond the matrix for cutting engagement with the formation being drilled. The cutting elements are oriented in rows radiating from a coolant aperture formed centrally of the bit outwardly about the entire cutting face defined by the matrix. The cutting elements are arranged to create closely spaced generally circular scratches in the formation for erosion thereof as the bit is rotated relative to the formation. A plurality of coolant courses are formed in the matrix and extend from the coolant passage in radiating manner and terminate radially intively thin high velocity film flowing over the entire smooth matrix surface disposed radially outwardly of the coolant courses for efficient cooling of each of the cutting elements and removal of cuttings eroded from the formation by the cutting elements.

11 Claims, 7 Drawing Figures PATENTl-InJuxzazsn SHEU 1 BF 2 F G. I

PRIOR, ART

FIG. 2 PRIOR ART FIG. 4

DRILLING BIT FOREARTH' FORMATIONS tion.

BACKGROUND OF THE INVENTION In the rotary drilling of bore holes inearth formations, relatively soft formations maybe drilled by using a fish tail bit having two or more blades that may be rotated against the formation to cut away portions of the formation as the bore hole is being drilled. A coolant fluid, commonly referred to as drilling mud, is circulated through a drill stem conduit to which the drill is attached and flows from apertures directing the coolant fluid at the area of contact between. the drilling bit and the earth formation. The coolant fluidserves. not only to cool the drilling bit duringthe drilling operation, but also to remove drilling cuttings that are eroded from the formation during the drilling process. The drilling cuttings may be removed from thedrilling fluid by passing'the drillingfluid through screening devices or by allowing the drilling cuttings to settle in a defined centrally through the bit structure and is typically conducted by coolant courses, defined by grooves formed in the cutting face of the drill bit, which serve to distribute the coolant fluid over the entire cutting face of the bit. The coolant courses, which may also be referred to as waterways, water courses, carriers, fluid grooves, magazines as well as a number of other terms, are recessed grooves that radiate across the face of the bit from the coolant passage or coolant source, in order to distribute the flowing coolant from the coolant passage over the cutting face of the bit.

ant courses. Varying the area of the coolant courses,

holding reservoir for the drilling fluid. After the drilling cuttings have been removed from the drilling fluid, the fluid maybe recirculated through the drill stem for cooling and-forremoval of drilling cuttings.

As earth formations are encountered that are relatively hard, it may be necessary to employ a rock bit incorporating a plurality of rollers having cuttingteeth formed thereon which are rotated against the formation for drilling purposes. Drilling fluid is circulated through the rock bit for cooling and for removal of dril ling cuttings in thesame manner as described above. Where hard earth formations are encountered during drilling, it may be appropriate to utilize a rotary bit generally referred to as a diamond, bit for drilling the earth formation. Diamond bits, of typical .construction, generally incorporate a drill bit body having a matrix of relatively hard material suchas tungsten carbide or any other suitable matrix material fixed thereto. A plurality of cutting elements, such as industrial diamonds, are typically embedded in the matrix material, with cutting portions thereof exposed above the matrix for cutting engagement with the formation being drilled; As the drill bit is rotated against the formation the cutting elements create a plurality of closely spaced scratches or .cuts in the formation eroding the formation away as the bore hole is being drilled.

As a diamond is rotated during a drilling operation, the cutting elements or diamondsare typically urged into the formation sufficiently to cause an optimum degree of penetration into the formation. As the bit rotates the diamond elements, being much harder than the formation being drilled, scratch or cut the formation away to define the'bore hole. Scratching or cutting by the cutting elements obviously develops a substantial amount of heat that must be dissipated in order to promote optimum operational life of the cutting elements of the bit. A coolant fluid, commonly referred to as drilling mud, is circulated through'a'coolant passage,

however, can result in controlled increase of fluid vecourses extend in radial relation between rows of cutting-elements and direct the coolant fluid in the area of the cutting elements to remove the heat that isdeveloped by the cutting elements as the formation is cut away. It has been determined, however, that the radiating coolant courses or channels direct the coolant fluid between the rows of cutting elements, but the direction and velocity of the coolant fluid prevents optimum cooling from taking place. It is difficult to cause the coolant fluid to divert from its direction of high velocity flow and circulate around each of the cutting elements because each of the coolant courses oneither side of the cutting elements is disposed at substantially the same pressure.

In order to cause the flowing coolant to leave its coolant course and flow across the cutting elements, it is nels are not connected to a fluid supply.. The nonsupplied coolant courses are of such configuration that they feed into the annulus of the bore hole about the drill bit. Coolant fluid, flowing from the high pressure primary coolant courses, which terminate short of the annulus, must cause a certain degree of cross-flow from the primary coolant courses to the non-supplied coolant courses and during such cross-flow the cutting elements are cooled and drilling cuttings are effectively removed by the coolant fluid.

It is therefore a primary object of the present invention to privide a novel bit structure that effectively eliminates the problem created by cross-flow of coolant fluid and effectively provides cooling capability for each of the cutting elements of the drill bit.

-It is another object of the present invention to provide a novel drill bit structure having an annular convex smooth cutting face with cutting elements embedded therein which is related to a plurality of radiating coolant courses in such manner as to evenlydistribute coolant fluid as a relatively thin high velocity film of coolant about the entire cutting face of the drill bit for effective cooling of each of the cutting elements embedded in the matrix defining the cutting face.

It is an evenfurtherobject of the present invention to provide a novel drill bit structure having anannular smooth cutting face that is of such configuration and disposition relative to a plane disposedgenerally normal to the axis'of the bore hole being drilled as to define an-annular line of tangency with the plane and includes' coolant courses extending from a centrally located coolant passage or supply which coolant courses terminate radially inwardly of the annular line'of tangency, thereby causing coolant to be distributed as a high velocity relatively thin film flowing over the entire 'of the drill bit for efficient cooling of each of a plurality of cutting elements embedded in the working face of .thebit. w

Other and further objects, features and advantages of the invention will become obvious to one-skilled in the art upon an understanding 'of the illustrative embodiment about to be described and various advantages, not referred to herein, will occur to one skilled in the art upon employment of the invention in practice.

BRIEF DESCRIPTION OF THE DRAWINGS I In order that the manner in which the above-recited advantages and objects of. the invention are attained as well as others which, will become apparent, can be understood in detail, more particular description of the invention, briefly summarized above, may be had by reference to the specific embodiments thereof, which are illustrated in the appendeddrawings, which drawings form a part of this specification. It is to be understood, however, that the appended drawings illustrate only typical embodiments of the invention and therefore are not to be considered to be limiting of its scope, for the invention may admit to other equally effective embodiments. v

In the drawings:

FIG. 1 is a fragmentary, partially sectioned isometricview of the cutting surface and coolant courses of a bit designed for promoting cross flow of coolant for cooling and cleaning purposes and representing at least a part of the prior art. v i r 1 FIG. 2 is a fragmentary sectional view taken through the bit structure of FIG. 1 and illustrating the coolant courses and cutting elements in diagrammatical manner.

FIG. 3 is an isometric view of a drill bit-constructed in accordance with the present invention.

FIG. 4 is an end view of the drill bit structureof FIG. 3.

FIG. 5 is a sectional view of the drill bit structure of FIGS. 3 and 4. FIG.. 6- is a fragmentary, partially section isometric view illustrating a portion of the cutting surface of the drill bit of F IGS. 3 and 4 and illustrating coolant fluid distribution by way of flow arrows.

FIG. 7is a fragmentary sectional view of the drill bit structure of FIGS. 3 and 4 illustrating the relationships of the cutting elements to the matrix material of the drill ,bit and to the formation being drilled.

evenly spaced manner along the surface of the conical SUMMARYOF THE INVENTION I The present invention is directed to the provision of a rotary drill bit for the drilling of bore holes through relative hard earth formations, which bit may comprise a body portion to which is adhered in any suitable manner a matrix defining a relatively smooth annular cutting face. A coolant passage may be formed in the drill body structure and may terminate at an aperture disposed centrally of the cutting face. The aperture may be of such configuration as to eliminate the develop- 'ment of a core during drilling operations. The cutting face may include a generally conical or belled portion having its apex'in communication with the aperture of the coolant passage and may curve into smooth merging relation with an annular convex portion of the matrix which convex portion may be presented in generally tangential relation with a plane disposed in generally normal relation with the axis of the bore hole being drilled. I

A plurality of coolant courses: maybe defined by grooves'formed in the matrix material and radiating in or belled/portion of the matrix. The coolant courses may extend from the coolant aperture along the conical portion of the matrix and may terminate radially inwardly of the'annular line of tangential relation between the cutting face of the matrix and a horizontal plane. v v

A plurality of cutting elements, such as industrial diamonds, are'embedded or otherwise received in fixed relation with-the matrix material and are-disposed in radiating rows extending from the apex of the conical portion of the cutting face throughout the surface area of the cutting face. The'cutting elements are also arranged to cut or otherwise form circular scratches in the formation as the bit is rotated relative thereto and -to erode away the formation, thereby developing the bore being drilled; As the cutting elements engage the formation, they penetrate the formation to a certain degree but maintain a spaced relation between the cutting face and the formation thereby defining a clearance through which coolant fluid may flow to achieve cooling andtremovalof drilling cuttings. Coolant fluid may betransmitted through the coolant courses andcaused to be distributed in a relatively thin high velocity film or layer about the entire surface area of the cutting face, thereby achievingefficient cooling of all of the cuttingelements and efficient removal of drilling cut- Referring nowto the drawings and first to FIG. 1 there is shownv a fragmentary cross-sectional view of a drilling bit representative of the prior art and teaching the use of supplied and non-supplied coolant courses for achieving cross-flow of coolant for efficient circulation of coolant about the cutting elements embedded in the matrix. The drill bit structure illustrated in FIG. 1 includes a drill bit body portion 10 to which may be secured matrix material 12 that is of a configuration to define a plurality of blades, such as shown at 14 and 16 and a plurality of supplied or high pressure coolant. courses, as shown at 18, 20 and 22 and a plurality of non-supplied or low pressure coolant courses, such as shown at 24. Cutting elements 26, which maybe industrial diamonds or may be composed of any other suit-.

able extremely 'hard 'substance', may be embedded in narily, the cutting elements will penetrate into the forthe matrix with cutting portions thereof exposed for cated on theblades l4 and 16 which define portions of 5 the cutting face of the drill bit.

The high pressure or supplied coolant courses, such as shown at 18, 20 and 22 are typically communicated with the source of coolant'in order to transport high pressure'coolant to various portions of the cutting face of the bit for even distribution about the working face for purposes of cooling and for removal of drilling cuttings. As explained above, the cutting elements are typically disposed on the blades on either side of a coolant course and, because of the velocity and pressure of the coolant fluid, it is difficult to cause the direction of the flow of coolant to change andflow across the blades for cooling of the cutting elements. The cutting elements,

non-supplied coolant courses are communicated with. the annulus of the well bore for conducting the heated and contaminated drilling fluid upwardly to the surface where it maybe cleansed, revitalized and recirculated into the'drill stem. Since-the high pressure coolant courses are not communicated with annulus, but are under high pressure, drilling fluid tends to flow from the high pressure coolant course across the blades, as shown by flow arrows 22in FIG. 6 and into the low pressure non-supplied coolant courses 24. Fluid crossing the blades in this manner obviously increases substantially in velocity because of the reduced dimension of the passages defined by the space between the formation and the cutting face 28 defined by the matrix. The coolantfluid flowing at increased velocity and crossing the cutting face of the bit, achieves effective cooling of those particular cutting elements disposed on the blades of the bit. Fluid flowing from the high pressure courses to the low pressure courses tends to channelize Trather than. becoming evenly distributed.

Those particular cutting elements, therefore, that are I disposed outof the channels the coolant fluid will take,

obviously will notreceive sufficient flow of coolant for optimum cooling. The inefficiently cooled cuttingelements will wear faster than the remaining cutting elements and will, in time, reduce the effective penetra tion rate of the bit to such point that replacement is n As shown in FIG. 2, which is a sectional view taken through the structure ofFIG. 1, the typical design criteria of this type of bit is' clearly evident. Cutting elements, such as industrial diamonds, have cutting portions thereof exposed above the cutting surface 28 of the matrix 12 by a distance, identified as A1. At any point in the cross section the total area of the coolant system for the cutting elements would be represented by the distance A2 because the cutting element exposure above the matrix is included in the area of the coolant system. The coolant area is, therefore, not restricted only to the volume A3 of the individual grooves or coolant courses defined in the matrix. The distance A1 however, the vertical height of the cutting elements above the cutting face 28, is reduced somewhat during operation of the bit because the cutting elements will have a certain amount of penetration into the formation the maximum of which is the distance A1. Ordimationby a variable distance A4 which is a distance less than the totalvertical height of the cutting elements above the cutting face.

Even where a condition of cross-flow is developed by high pressure and low pressure coolant courses in the manner described above, only a part of the cutting elements will be cfficiently cooled. For example, with reference to FIG. 1, it is obvious that cross-flow will occur essentially as shown by the flow arrows 23. The cutting elements however disposed upstream of the low pressure coolant course will not be subjected to cross flow and therefore the terrific heat build up during drilling operations will not be efficiently dissipated. The cutting elements therefore will tend to wear much faster than the efficiently cooled cutting elements disposed in the area-of cross-flow. Moreover, if the bit is subjected to substantial pressure during the drilling operation penetration of the cutting elements into the formation may be total, equaling the distance A1 and therefore, there can be no flow of coolant circulating from the coolant coursesabout the cutting elements and the cutting elements, therefore, will-receive virtually no cooling while the cutting operation is taking place. Reducing the dimension of the coolant system about the bit structure by the distance A1 during complete penetration of the cutting elements into formation obviously has the effect of increasing the velocity of fluid flow in the coolant courses, but flow of coolant fluid must occur at each of the cutting elements for efficient cooling. The

coolant fluid therefore must be caused to leave the coolant courses in order to remove heat from the cutting elements. I

' DESCRIPTION OF PREFERRED EMBODIMENT With reference now to FIGS. 3-7, the present invention is shown to provide structure to achieve efficient coolant flow to each of the cutting elements of the bit regardless of the degree of penetration of the cutting elements into the formation. As shown in FIGS. 3, 4 and 5, a drilling bit constructed in accordance with the present invention and illustrated generally at 30, will incorporate -a body portion 32 having an upper threaded extremity 34 for attachment of the bit to' the lower internally threaded extremity of a section of drill stem, not shown. The body portion 32 of the drill bit is provided with a centrally disposed bore 36, adapted to communicate coolant fluid from the drill-stem to which the drill isconnected andto direct the drilling fluid toward the lower extremity of the drill bit. The bore 36 terminates at an aperture 38 which, as shown in FIG.

4, is of irregular, generally triforrn configuration in order to prevent the development of a core as a drilling operation as conducted.

It will be desirable, in order to provide the bit 30 with the capability of firmly supporting cutting elements such as'industrial diamonds, to provide the bit with a covering in which the cutting elements may be embedded. The body portion of the bit 32 is generally composed of a relatively hard substance such as steel, forexample, to which cutting elements such as industrial diamonds will not readily adhere. In accordance with the present invention, means for securing the cutting elements may conveniently take the form of a matrix 40 that may be secured to the body structure of the bit in any suitable manner. The matrix may be composed of any suitable substance, such as tungsten carbide or any other suitablehardinetallic substance' or, if dealso have a wear resistant characteristic regardless of its metallic or plastic composition. I

In accordance with the principles of the present invention, it is desirable to produce a drill bit structure having the capability of evenly distributing coolant fluid from a fluid supply source about a cutting surface and to cause the velocity of the flowing fluid to be greatly increased as compared with the velocity of coolant fluid flowing from the aperture of the bit in order to provide arelatively thin and evenly distributed film of coolant flowing at extremely highvelocity for efficient cooling of each of the cutting elements embedded in the matrix of the bit. a

As drilling occurs at greater depth it is necessary that the velocity of the flowing drilling fluid be maintained as high as possible. Friction losses and other variables such as fluid area caused by diamond exposure, and the decrease in totalfluid escape area toward the outer periphery of the bit have the effect f reducing the velocity of the flowing drilling fluid. It is necessary that fluid velocity be high enough to achieve an appropriate degree of cooling and high enough to transport the cuttings away from the cutting elements to prevent interference with further cutting action. In accordance with the present invention, therefore, the matrix 40 of the bit structure is designed to present a smooth cutting face 42 and the cutting elements extend from the matrix beyond-this smooth cutting face to a degree necessary for optimum cutting. The matrix may be cast upon the body of the .bit ifdesired andwill be of such structural integrity as to provide for secure retentionof the cutting elements. It may also be desirable that the matrix material be capable of wearing to some extent thereby further exposing the cutting elements that are embedded therein as the cutting elements become worn. The matrix material may also be .of suitable thickness to provide ample strength for optimum retention of the cutting elements. I As shown inFIG. 5, the matrix material 40 is formed to define the aperture38 and extends from the aperture downwardlyto define a'generally belled'or conical portion 44 extending downwardly and curvilinearly into smooth transitional relationship with a tangential portion 46.' The tangential portion is of annular configuration and is disposed in generally tangential relationship with an imaginary plane 48 extending the normal to the axis of the bore hole'drilled by'he bit. The matrix ex.- tends upwardly from the tangential portion 46 in smooth annular curvilinear manner to a side wall por tion 50. The conical or belled portion 44, the tangential portion 46 and thesidewall portion 50 cooperate to define the cutting face 42 of the bit.

face where the-particles may be removed before recir- 'present invention such coolant courses may conveniently take the form illustrated in FIGS. 3, 4 and 5, for

Y example, wherethe coolant courses are shown as being defined by curvilinear grooves 52 formed in the matrix material and radiating downwardly and outwardly in curvilinear manner on the conical portion 44 of the cutting face. As indicated above, the matrix material is provided with. a tangentialportion 46 which as indicated in FIGS. 4 and 5 is disposed relativetg an imaginary plane 48 to define an annular line of tangency 54 on the cutting face of the matrix. The coolant courses '52 defined by straight grooves 62 and branched grooves 63 extend from the aperture 38 and terminate radially inwardly of the annular line of tangency 54 in order to provide a substantial volume of high pressure coolant fluid at an area immediately radially inwardly of the primary bearing portion of the bit defined by the annular line of tangency. As the high pressure coolant fluid is forced from the coolant courses or grooves 52 into the relatively thin space between the formation and the smooth outer surface defined by the cutting face 42 of the matrix, the pressure of the fluid will not diminish "substantially but the velocity of the fluid will increase materially and the fluid will be evenly distributed as a relatively thin layer of coolant fluid flowing at extremely high velocity. 7 a

The cutting elements, which may be industrial diamonds or may be of any other suitable composition, extend in rows from the aperture 38 in radiating manner about the entire surface area defined by the matrix and are oriented to develop closely spaced or overlapping circular scratches in the formation as the bit is rotated, thereby'eroding the formation. High velocity coolant fluid also. serves to transport cuttings, broken or cut away from the formation, away from the cutting elements and thereby maintain the area being drilled as clean as possible to prevent interference with the cutting action of the cuttingelements. The particles of the formation eroded away during a'drilling operation will be transported upwardly by the coolant fluid to the surculation of the coolant fluid through the drill stem;

*In the area of the-belledor conical portion .44 of the matrix, that portion-of the matrix remaining between the grooves 52 defines a plurality of blades 56 that assist the cutting elements in cutting'away the formation as the bit is rotated. The substantial volume of high pressurecoolant available in the belled portion of the As indicated above, it is desirable to conduct c oolant I to provide ample coolant fluid for the cutting face, it isv desirable to provide a plurality of radiating channels or coolant courses through whichthe coolant fluid may be distributed in radial manner. In accordance with the bit provides effective cooling for the cutting elements located in the belled portion while cooling of the remaining cutting elements is enhanced by circulation of a thin film of high velocity-fluidaround each cutting element in the manner. described hereinbelow.

With reference to FIG. 5, it should be noted that each of the grooves 52 is tapered at the downstream portion thereof which causes the flowing coolant fluid therein to substantially increase in velocity immediately before being forced from the groove. Also, the tapered portion of the grooves causes the coolant material to be distributed as a thin layer in the pace defined between the formation and the smooth cutting face of the bit and to substantially increase in velocity as it reaches the small coolant space defined between the cutting face of the bit. andthe formation. FIG. 7 is representative of the tapered terminal portions of the grooves 52 and is descriptive of the manner in which the coolant fluid is distributed asit leaves thev coolant courses. In FIG. 7 the coolant chamber or space A1 is that portion defined between the formation 58 and the cutting space 42. As

' that as the space Al decreases, the velocity of the fluid flowing through the space increases proportionately and therefore the effective cooling caused by the increase of velocity of the flowing fluid effectively offsets the increased amount of heat generated by increased penetration of the cutting element 60 into the formation.

It has been determined that there exists a critical ratio of the cuttingelements, when industrial diamonds are utilized as cutting elements,.which ratio is not expressed in terms of stones per square inch,.but rather it is expressed as a total number for a wide range of bit sizes. For'example, it has been determined that a bit constructed inaccordance with the present invention will require from 210 to 350 industrial diamonds in all bit sizes from 5% inches to 8% inches. vIf the number'of stones falls below or exceeds the range indicated above, penetration rates and bit wear will be adversely affected. The invention, therefore, concerns not only the construction of the bit, as indicated above, but incorporation of a specific numerical range'of stones for bits following within a particular size range.

It has also been determined that the provision of radial blades with industrial diamonds or other suitable cutting elements embedded within the blades or ribs and extending outwardly therefrom, is adversely affected if the blades extend in the area of tangency-between the. annular portion of the. bit and-a horizontal plane disposed substantially normal to the axis of the bore hole formed by the bit. Channelization of the coolant fluid caused by the radiating blades and grooves has been found to cause insufficient cooling to occur in the area of tangency, identified above.

It is desirable to transport the flowing c oolant fluid in substantial volume to an annular area of the bit radially inwardly of the point of tangency, described above. Because of the generally triangular configuration of the aperture. 38, straight coolant courses extending from the extremities of the generally triangular aperture would not ordinarilyv supply sufficient flow of coolant fluid to those portions of the cutting face drill bit opposite the extremities of the aperture while straight coolant courses extending from the central portion of the aperture could quite easily supply coolant fluid to the remaining opposed portions of the drill bit because of the greater supply of coolant fluid at the central portion of the aperture. This would facilitate development of hot spots on the cutting face, that could accelerate bit wear. Accordingly; the plurality of generally straight coolant courses 62 may extend from the central portion of the aperture 38 while the plurality of branched cool the extremity be a branch of a coolant course extending from one of the extremities of the aperture or a straight coolant course extending from the central portion of feature provides for optimum flow at maximum velocity as a relatively thin high velocity layer or film of coolant fluid, as the fluid flows outwardly from the coolant courses and across the tangential area of the drill bit.

The cutting elements are efficiently cooled by the high velocity flow of coolant medium and drilling cuttings eroded from the formation by the cutting elements are efficiently transported away from the immediate area of the cutting elements to prevent interference with further cutting.

in view of the foregoing it is apparent that l have provided a novel drill bit structure for drilling bore holes in earth formations that are difficult to drill and incorporating hard cutting elements, such as industrial diamonds or the like, embedded in the drill bit structure ting face of the drill bit and'causes the development of a relatively thin film of coolant fluid flowing at extremely high velocity for cooling and cleaning purposes. Moreover, fluid velocity decrease at maximum drilling depths is not materially'decreased and the total,

hydraulic energy developed by the bit will be maintained at a high and functional level at all times to facilitate drilling at penetration rates not ordinarily obtainable by other bit structures. A drill bit manufactured in accordance with the present invention will have an optimum rate of penetration, not only because of its cooling and cleaning capabilities,but also becauseof incorporation of an optimum number of cutting elements in the cutting face of'the bit and optimum radial layout of cutting elements to promote efficient cooperative cutting. Drill bits, manufactured-in accordance with the present invention, are of simple nature, are extremely reliable in use and do not exceed the cost of other drill bits-having similar qualities;

scription of the apparatus itself. It will be understoodthat certaincombinations and-subcombinations are of utility and may be employed without reference to other the apperture. In this manner, equal flow of coolant is 6 directed in efficient manner toward all parts of the cutting face of the bit and there will be no tendency for the bit to develop hot spots during drilling operations. This features and subcombinations. This is contemplated by and is within the scope of the present invention.

As many possible embodiments may be made of this invention without departing from the spirit or scope thereof, it is to be understood that all matters, herein- 'above set forth or shown in the accompanying drawings, are to be interpreted as illustrative and not in any limiting sense.

I claim: 7 l. A drill bit for drilling bore holes in relatively hard earth formations comprising:

a drill bit body having coolant passage means defined therethrough and defining a coolant outlet; matrix material being provided on said drill bit body and defining a smooth annular cutting face having a tangent portion adapted to be disposed in gener- 1.1 ally tangential relation with a horizontal plane and having a generally conical portion curving smoothly into merging relation with tangent portion,'the apex of said conical portion being disposed in communication with said coolant passage means;

a plurality of coolant courses-being defined in said conical portion of said matrix material and extending in radiating relation from said outlet of said coolant passage means along said conical portion, said coolant courses terminating radially inwardly of an annular line of tangency definedby the tangential relation of said tangent portion with said horizontal plane; and

a plurality of cutting elements being disposed'in fixed relation with said matrix material and having cutting portions thereof exposed above the surfaces of said cutting face for eroding contact with said earth formation.' 2; A drill bit as recited in claim 1: said cutting elements being arranged in radiating rows. from the apex of said conical portion past said tangent portion and upwardly over the entire matrix portion, said cutting elements being oriented to generate closely oriented circular scratches in said formation for cutting away the formation upon rotation of the bit.

3. A drill bit as recited in claim 1:

said cutting elements being industrial diamonds partially' embedded in said matrix material.

4. A drill bit as recited in claim 1': v

radiating blade elements being defined by said coolant courses and extending'from a point adjacent I said coolant passage means to points located radially inwardly of said annular line of tangency.

5. A drill bit as recited in claimol:

said cutting elements being industrial diamonds partially embedded in said matrix material and having cutting portions thereof extending beyond said cutting face for erosive contact with said formation and cooperating with. said formation to define a coolant circulation space about the entire cutting face ofthe bit; x Q ya plurality of blade elements being defined by said coolant courses in said conical portion of said bit and extending in radiating manner from said coolant aperture toward said tangent portion of the cutting face; and the cutting elements in said conical portion being disposed in radiating rows on said blade elements. 6. A drill bitas' recited in claim 1: said bit having a size range of 5% inches to 8% inches in diameter and having'frorn 21-0 to 350 cutting elements provided thereon. 7. A method of rotary drilling a bore hole in a relatively hard earth formation,'utilizing a'drill bit having a body portion defining a smooth annular cutting face having a plurality of rows of cutting elements embedded therein with portions thereof exposed for erosive contact with the formation, said annular cutting face including-a lowermost annular portion defining an annular line of tangency with a plane disposed substantially normal to the axis of the bore hole beingdrilled, said bit having a plurality of coolant distribution courses extending in radiating manner from a centrally located coolant aperture and terminating radially inwardly. of saidannular line of tangency, said method comprising: rotating said rotary bit against said earth formation to cause said cutting elements of said bit of cut closely oriented circular scratches in the formation thereby'eroding said formation and forming said bore hole;

directing a flow of coolant fluid from said coolant aperture into said coolant distribution courses;

directing a flow of coolant fluid through said coolant courses to an annular area of said cutting face disposed radially in inwardly of said annular line of tangency; and

directing a thin even high velocity film of coolant fluid from said coolant distribution courses over the entire surface area of said disposed radially outwardly of said annularline of tangency for cooling of said cutting elements and removal of cuttings eroded by said cutting elements from said formatron.

8. A- drill bit for rotary drilling of bore holes in rela- 3 tively hard earth formations wherein a coolant fluid is --caused to flow under pressure through said drill bit during'drilling, said drill'bit comprising:

a drill bit body defining a cutting face, said cutting face having an annular smoothly curved convex portion defining an annular line of tangency with a horizontal plane disposed in substantially normal relation to theaxis of the bore hole being drilled;

coolant passage means being defined centrally through said drill bit body and terminating in a I coolant aperture; A r V a plurality of cutting elements being carried by said drill bit body and being disposed in rows throughout the cutting face of said bit, said rows radiating from said coolant aperture; and

a plurality of coolant courses formed in said cutting face and extending radially outwardly from said coolant aperture towardsaid annular line of tangency with said horizontal plane and terminating radially inwardly of said annular line of tangency.

9. A drill bit as recited in claim 8:

'said cutting elements being arranged to cut a plurality of closely related generally circular scratches in said formation during rotation of said bit relative to said formation; and

coolant fluid being conducted to the portion of said cutting face disposed radially outwardly of said annular line of tangency, increasing in velocity and flowing as'a relatively thin film about each of the cutting elements for the purpose of cooling and for removal of cuttings eroded from said formation.

10. A drill bit as recited in claim 8:

radiating blade elements being defined by said coolant courses and extending from a point adjacent said coolant passage means to points located radially inwardly of said annular line of tangency.

11. A drill bit as recited in claim 8:

coolant fluid being conducted tosaid annular line of tangency increasing in velocity and flowing as a relativel'y thin film about each of said cutting elements for purposes of cooling and for removal of cuttings eroded from said formation by said cutting elements; and

radiating blade elements being defined by said coolant courses and extending from a coolant aperture, said coolant courses terminating radially inwardly of said annular line of tangency. 

1. A drill bit for drilling bore holes in relatively hard earth formations comprising: a drill bit body having coolant passage means defined therethrough and defining a coolant outlet; matrix material being provided on said drill bit body and defining a smooth annular cutting face having a tangent portion adapted to be disposed in generally tangential relation with a horizontal plane and having a generally conical portion curving smoothly into merging relation with tangent portion, the apex of said conical portion being disposed in communication with said coolant passage means; a plurality of coolant courses being defined in said conical portion of said matrix material and extending in radiating relation from said outlet of said coolant passage means along said conical portion, said coolant courses terminating radially inwardly of an annular line of tangency defined by the tangential relation of said tangent portion with said horizontal plane; and a plurality of cutting elements being disposed in fixed relation with said matrix material and having cutting portions thereof exposed above the surfaces of said cutting face for eroding contact with said earth formation.
 2. A drill bit as recited in claim 1: said cutting elements being arranged in radiating rows from the apex of said conical portion past said tangent portion and upwardly over the entire matrix portion, said cutting elements being oriented to generate closely oriented circular scratches in said formation for cutting away the formation upon rotation of the bit.
 3. A drill bit as recited in claim 1: said cutting elements being industrial diamonds partially embedded in said matrix material.
 4. A drill bit as recited in claim 1: radiating blade elements being defined by said coolant courses and extending from a point adjacent said coolant passage means to points located radially inwardly of said annular line of tangency.
 5. A drill bit as recited in claim 1: said cutting elements being industrial diamonds partially embedded in said matrix material and having cutting portions thereof extending beyond said cutting face for erosive contact with said formation and cooperating with said formation to define a coolant circulation space about the entire cutting face of the bit; a plurality of blade elements being defined by said coolant courses in said conical portion of said bit and extending in radiating manner from said coolant aperture toward said tangent portion of the cutting face; and the cutting elements in said conical portion being disposed in radiating rows on said blade elements.
 6. A drill bit as recited in claim 1: said bit having a size range of 5 7/8 inches to 8 3/4 inches in diameter and having from 210 to 350 cutting elements provided thereon.
 7. A method of rotary drilling a bore hole in a relatively hard earth formation, utilizing a drill bit having a body portion defining a smooth annular cutting face having a plurality of rows of cutting elements embedded therein with portions thereof exposed for erosive contact with the formation, said annular cutting face including a lowermost annular portion defining an annular line of tangency with a plane disposed substantially normal to the axis of the bore hole being drilled, said bit having a plurality of coolant distribution courses extending in radiating manner from a centrally located coolant aperture and terminating radially inwardly of said annular line of tangency, said method comprising: rotating said rotary bit against said earth formation to cause said cutting elements of said bit of cuT closely oriented circular scratches in the formation thereby eroding said formation and forming said bore hole; directing a flow of coolant fluid from said coolant aperture into said coolant distribution courses; directing a flow of coolant fluid through said coolant courses to an annular area of said cutting face disposed radially in inwardly of said annular line of tangency; and directing a thin even high velocity film of coolant fluid from said coolant distribution courses over the entire surface area of said disposed radially outwardly of said annular line of tangency for cooling of said cutting elements and removal of cuttings eroded by said cutting elements from said formation.
 8. A drill bit for rotary drilling of bore holes in relatively hard earth formations wherein a coolant fluid is caused to flow under pressure through said drill bit during drilling, said drill bit comprising: a drill bit body defining a cutting face, said cutting face having an annular smoothly curved convex portion defining an annular line of tangency with a horizontal plane disposed in substantially normal relation to the axis of the bore hole being drilled; coolant passage means being defined centrally through said drill bit body and terminating in a coolant aperture; a plurality of cutting elements being carried by said drill bit body and being disposed in rows throughout the cutting face of said bit, said rows radiating from said coolant aperture; and a plurality of coolant courses formed in said cutting face and extending radially outwardly from said coolant aperture toward said annular line of tangency with said horizontal plane and terminating radially inwardly of said annular line of tangency.
 9. A drill bit as recited in claim 8: said cutting elements being arranged to cut a plurality of closely related generally circular scratches in said formation during rotation of said bit relative to said formation; and coolant fluid being conducted to the portion of said cutting face disposed radially outwardly of said annular line of tangency, increasing in velocity and flowing as a relatively thin film about each of the cutting elements for the purpose of cooling and for removal of cuttings eroded from said formation.
 10. A drill bit as recited in claim 8: radiating blade elements being defined by said coolant courses and extending from a point adjacent said coolant passage means to points located radially inwardly of said annular line of tangency.
 11. A drill bit as recited in claim 8: coolant fluid being conducted to said annular line of tangency increasing in velocity and flowing as a relatively thin film about each of said cutting elements for purposes of cooling and for removal of cuttings eroded from said formation by said cutting elements; and radiating blade elements being defined by said coolant courses and extending from a coolant aperture, said coolant courses terminating radially inwardly of said annular line of tangency. 